To provide a treater capable of accurately discriminating the right and wrong of the posture of a substrate held by a substrate holding part regardless of the diameter enlargement of the substrate, being unrelated to a problem such as the difficulty of the optical axis adjustment of a light receiving part and performing accurate detection at all times without being affected by the surface state of the substrate just by providing a single sensor.

This processor is provided with an ultrasonic wave sensor 22 constituted of an ultrasonic wave irradiation part of irradiating the surface of the substrate W held by the substrate holding part 10 with ultrasonic waves and an ultrasonic wave reception part for receiving the ultrasonic waves emitted from the ultrasonic wave irradiation part and reflected on the surface of the substrate. Whether or not the posture of the substrate is normal is judged depending on whether or not the ultrasonic waves emitted from the ultrasonic wave irradiation part and reflected on the surface of the substrate are received in the ultrasonic wave reception part.